1. Field of the Invention
The invention is generally related to chemical-mechanical polishing operations performed during integrated circuit manufacturing, and particularly to polishing semiconductor wafers and chips which include integrated circuits. The invention is specifically related to polishing pad construction and operations that allow for improved control of polishing.
2. Description of the Related Art
Chemical-mechanical polishing (CMP) is performed in the processing of semiconductor wafers and/or chips on commercially available polishers, such as the Westech 372/372M polishers. The standard CMP tools have a circular polishing table and a rotating carrier for holding the substrate.
Generally, CMP does not uniformly polish a substrate surface, and material removal proceeds unevenly. For example, it is common during oxide polishing for the edges to the wafer to be polished faster than the center of the wafer. Although the reasons for this phenomenon are not clearly understood, insufficient slurry coverage of the polishing pad, and/or poor resiliency of the polishing pad, and/or the shape of the wafer carrier may all contribute to the problem.
Various methods have been attempted, with only limited success, to achieve uniform material removal from substrates by CMP. For example, the slurry coverage has been improved using pad conditioning. However, the conditioning apparatus can leave large particles on the pad which then cause scratches on the substrate. It is also possible to modify the shape of the wafer carrier, however, the shape which works well with one polishing pad may work poorly with another pad. In addition, modification of the shape of the wafer carrier may preclude the use of a two-table process in which different polishing pads and/or processes are used.
In addition, it is common for polishing pads to include a uniform pattern of perforations or embossed areas across the pad so that the slurry is brought on to the surface of the pad. The continuous pattern across the pad produces some improvement in the polishing action but does not correct the center to edge polishing variations across a substrate.
It is also difficult to control the CMP removal profile so that desired portions of a substrate are polished at faster rates than other portions.
In light of the foregoing, there exists a need for a method and device for controlling the removal of material from substrate such as semiconductor wafers and/or chips such that a uniform surface across the substrate can be achieved or such that materials from different portions of a substrate can be removed at different rates.